A battery is an interconnection of a plurality of galvanic cells, of the same type, as a rule, and it represents an electrochemical energy store and an energy converter, which is provided to output electrical energy. In the battery, during discharge, stored chemical energy is converted to electrical energy by the electrochemical reaction, for this purpose. In this process, the cells of the battery, which may be connected in parallel or in series or in a mixed fashion, are situated in so-called modules. One or more of these modules, connected in series or in parallel, form the battery.
As to the cells mentioned, one may distinguish between primary cells, that are not rechargeable, and secondary cells, that are rechargeable. A rechargeable battery is also designated as an accumulator having accumulator cells. In the following, the term battery is intended to include both a non-rechargeable battery, as well as a rechargeable battery.
Batteries are used, for example, in motor vehicles for providing the electric current for the starter of the internal combustion engine. Such a battery is designated as a starter battery and is developed as a lead accumulator, for instance. Besides supplying the starter, the battery also supplies the other electrical users in the vehicle. For starting the internal combustion engine, high currents are briefly required which also have to be provided at low temperatures. In electric vehicles or hybrid vehicles, batteries are also used as energy sources for driving the vehicle. These are also designated as traction batteries.
In each case it is required that the functional capability of the battery in the vehicle be monitored regularly or even continually, in order to ensure a reliable operation of the motor vehicle. For this purpose, characteristic variables and operating variables of the battery are picked up, such as the terminal voltage, the temperature, the pressure, particularly the internal pressure of the cell, the current, the impedance, etc.
It is believed to be understood that one may use sensors in the battery for monitoring and communication. Furthermore, it is believed to be understood that, inside the battery, one may record sensor signals via data lines provided for this, such as the CAN bus, which is used typically in motor vehicles.
Document WO 2009/149690 A1 discusses a battery having battery cells and a method for monitoring the battery. The battery presented there has a plurality of battery cell stacks, a battery cell stack being able to have a single battery cell or to be constructed of battery cells connected in parallel. Sensors monitor the charge state of individual battery cells. A charge compensation device is assigned to the described battery, which has a target value table of the admissible charge states of individual batteries. The charge compensation device varies the charge compensation as a function of the charge state.
When the target value for the charge state of individual battery cells is reached, the charge compensation of the battery cells is interrupted. On each battery cell, a tapping is situated for a charge compensation line, the charge compensation arrangements being unified in a wiring harness and being supplied to provided cell monitoring modules which, on their part, have sensors and cell monitoring circuits, these components of the cell monitoring being situated in common in the charge compensation device, spatially separated from the battery cells.